Semiconductor memory device

ABSTRACT

According to the embodiment, a semiconductor memory device includes a first conductive layer, a second conductive layer, a first memory cell, a second memory cell, a third conductive layer, a first contact, a intermediate memory cell, a fourth conductive layer, a third memory cell, a fifth conductive layer, and a second contact. The third conductive layer is separated from the first conductive layer and the second conductive layer in a third direction crossing a first direction and crossing a second direction and extends in the second direction. The fifth conductive layer is separated from the second conductive layer in the third direction and extends in the second direction. A first length of the second conductive layer along the second direction is shorter than a second length of the fifth conductive layer along the second direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityfrom U.S. Ser. No. 16/845,538, filed Apr. 10, 2020, which is acontinuation of U.S. Ser. No. 16/282,482, filed Feb. 22, 2019, which isa continuation of U.S. Ser. No. 15/899,465, filed Feb. 20, 2018, whichis a continuation of U.S. Ser. No. 15/384,501, filed Dec. 20, 2016,which is a continuation of U.S. Ser. No. 15/069,378 filed Mar. 14, 2016,and claims the benefit of priority of U.S. Provisional PatentApplication 62/216,176 filed Sep. 9, 2015; the entire contents of eachof which are incorporated herein by reference.

FIELD

An embodiment relates to a semiconductor memory device.

BACKGROUND

A cross-point semiconductor memory device in which two conductive layersand a resistance-change layer provided between the layers are providedhas been proposed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B are schematic sectional views illustrating asemiconductor memory device according to an embodiment;

FIG. 2A is a schematic sectional view illustrating the semiconductormemory device according to the embodiment;

FIG. 2B is a schematic sectional view illustrating the semiconductormemory device according to the embodiment;

FIG. 3A is a schematic sectional view illustrating the semiconductormemory device according to the embodiment;

FIG. 3B is a schematic sectional view illustrating the semiconductormemory device according to the embodiment;

FIG. 4 is a schematic sectional view illustrating the semiconductormemory device according to the embodiment; and

FIG. 5 is a schematic sectional view of another example of thesemiconductor memory device according to the embodiment.

DETAILED DESCRIPTION

According to one embodiment, a semiconductor memory device includes afirst-layer first-row first conductive layer, a first-layer second-rowfirst conductive layer, a first-layer first-row memory cell, afirst-layer second-row memory cell, a first-layer first-row secondconductive layer, a first-layer first-row contact, a second-layerfirst-row intermediate memory cell, a second-layer first-row firstconductive layer, a second-layer first-row memory cell, a second-layerfirst-row second conductive layer, and a second-layer second-rowcontact. The first-layer first-row first conductive layer extends in afirst direction. The first-layer second-row first conductive layer isseparated from the first-layer first-row first conductive layer in asecond direction crossing the first direction and extends in the firstdirection. The first-layer first-row second conductive layer isseparated from the first-layer first-row first conductive layer and thefirst-layer second-row first conductive layer in a third directioncrossing the first direction and crossing the second direction andextends in the second direction. The first-layer first-row memory cellis provided between the first-layer first-row second conductive layerand the first-layer first-row first conductive layer. The first-layersecond-row memory cell is provided between the first-layer first-rowsecond conductive layer and the first-layer second-row first conductivelayer. The first-layer first-row contact is connected to the first-layerfirst-row second conductive layer. The first-layer first-row contactextends in the third direction between the first-layer first-row firstconductive layer and the first-layer second-row first conductive layer.The second-layer first-row second conductive layer is separated from thefirst-layer first-row second conductive layer in the third direction andextends in the second direction. The second-layer first-row secondconductive layer the first-layer first-row second conductive layer isdisposed between the second-layer first-row second conductive layer andthe first-layer first-row memory cell and between the second-layerfirst-row second conductive layer and the first-layer second-row memorycell in the third direction. The second-layer first-row intermediatememory cell is provided to between the first-layer first-row secondconductive layer and the second-layer first-row second conductive layer.The second-layer first-row first conductive layer is provided betweenthe second-layer first-row intermediate memory cell and the second-layerfirst-row second conductive layer and extends in the first direction.The second-layer first-row memory cell is provided between thesecond-layer first-row first conductive layer and the second-layerfirst-row second conductive layer. The second-layer second-row contactis connected to the second-layer first-row second conductive layer. Thesecond-layer second-row contact is separated from the first-layerfirst-row contact in the second direction and extends in the thirddirection. The first-layer second-row first conductive layer and thefirst-layer second-row memory cell are disposed between the second-layersecond-row contact and the first-layer first-row contact in the seconddirection. A first length of the first-layer first-row second conductivelayer along the second direction is shorter than a second length of thesecond-layer first-row second conductive layer along the seconddirection.

Embodiments of the invention will be described hereinafter withreference to the drawings.

The drawings are schematic and conceptual, and the relationships betweenthe thickness and width of portions, the size ratio among portions,etc., are not necessarily the same as the actual values thereof.Further, the dimensions and proportions may be illustrated differentlyamong drawings, even for identical portions.

In the present specification and drawings, the same elements as thosedescribed previously with reference to earlier figures are labeled withlike reference numerals, and the detailed description thereof is omittedas appropriate.

Embodiment

FIG. 1A and FIG. 1B are schematic sectional views illustrating asemiconductor memory device according to an embodiment.

FIG. 1B is the schematic sectional view along line B1-B2 in FIG. 1A.

As shown in FIG. 1A and FIG. 1B, a semiconductor memory device 110according to the embodiment includes a first block BK1 (first layerblock), a second block BK2 (second layer block), a third block BK3(third layer block) and a fourth block BK4 (fourth layer block). Theseblocks each includes a conductive layer and a memory cell. Theconductive layer and the memory cell of the second block BK2 areprovided on the first block BK1. The conductive layer and the memorycell of the third block BK3 are provided on the conductive layer and thememory cell of the second block BK2. The conductive layer and the memorycell of the fourth block BK4 are provided on the conductive layer andthe memory cell of the third block BK3. Contacts extending in thevertical directions are provided on each of the blocks.

As below, the first block BK1 and the second block BK2 will bedescribed.

The semiconductor memory device 110 includes a first-layer first-rowfirst conductive layer B11, a first-layer second-row first conductivelayer B12, a first-layer first-row memory cell CE11, a first-layersecond-row memory cell CE12, a first-layer first-row second conductivelayer W11, a first-layer first-row contact CT11, a second-layerfirst-row intermediate memory cell MC21, a second-layer first-row firstconductive layer B21, a second-layer first-row memory cell CE21, asecond-layer first-row second conductive layer W21, and a second-layersecond-row contact CT22.

The first-layer first-row first conductive layer B11 extends in a firstdirection Dr1. The first-layer second-row first conductive layer B12 isseparated from the first-layer first-row first conductive layer B11 in asecond direction Dr2 crossing the first direction Dr1 and extends in thefirst direction Dr1.

The first-layer first-row second conductive layer W11 is separatelyprovided from the first-layer first-row first conductive layer B11 andthe first-layer second-row first conductive layer B12 in a thirddirection Dr3 crossing the first direction Dr1 and crossing the seconddirection Dr2. The first-layer first-row second conductive layer W11extends in the second direction Dr2.

The first direction Dr1 is e.g. the Y-direction. The second directionDr2 is e.g. the X-direction. The third direction Dr3 is e.g. theZ-direction.

The first-layer first-row memory cell CE11 is provided between thefirst-layer first-row second conductive layer W11 and the first-layerfirst-row first conductive layer B11. The first-layer second-row memorycell CE12 is provided between the first-layer first-row secondconductive layer W11 and the first-layer second-row first conductivelayer B12.

The first-layer first-row contact CT11 is connected to the first-layerfirst-row second conductive layer W11. The first-layer first-row contactCT11 extends in the third direction Dr3 between the first-layerfirst-row first conductive layer B11 and the first-layer second-rowfirst conductive layer B12.

The second-layer first-row second conductive layer W21 is separated fromthe first-layer first-row second conductive layer W11 in the thirddirection Dr3 and extends in the second direction Dr2. The first-layerfirst-row second conductive layer W11 is disposed between thesecond-layer first-row second conductive layer W21 and the first-layerfirst-row memory cell CE11 and between the second-layer first-row secondconductive layer W21 and the first-layer second-row memory cell CE12 inthe third direction Dr3.

The second-layer first-row intermediate memory cell MC21 is providedbetween the first-layer first-row second conductive layer W11 and thesecond-layer first-row second conductive layer W21.

The second-layer first-row first conductive layer B21 is providedbetween the second-layer first-row intermediate memory cell MC21 and thesecond-layer first-row second conductive layer W21 and extends in thefirst direction Dr1.

The second-layer first-row memory cell CE21 is provided between thesecond-layer first-row first conductive layer B21 and the second-layerfirst-row second conductive layer W21.

The second-layer second-row contact CT22 is connected to thesecond-layer first-row second conductive layer W21. The second-layersecond-row contact CT22 is separated from the first-layer first-rowcontact CT11 in the second direction Dr2 and extends in the thirddirection Dr3.

The first-layer second-row first conductive layer B12 and thefirst-layer second-row memory cell CE12 are disposed between thesecond-layer second-row contact CT22 and the first-layer first-rowcontact CT11 in the second direction Dr2. In the second direction Dr2, athird portion W11 c of the first-layer first-row second conductive layerW11 is disposed between the second-layer second-row contact CT22 and thefirst-layer first-row contact CT11.

A first length L1 of the first-layer first-row second conductive layerW11 along the second direction Dr2 is shorter than a second length L2 ofthe second-layer first-row second conductive layer W21 along the seconddirection Dr2.

The first-layer first-row first conductive layer B11 is e.g. a bit lineBL. The first-layer first-row second conductive layer W11 is e.g. a wordline WL. The first-layer first-row memory cell CE11 is provided betweenthe first-layer first-row first conductive layer B11 and the first-layerfirst-row second conductive layer W11.

For instance, when a voltage VT is applied between the first-layerfirst-row first conductive layer B11 (bit line BL) and the first-layerfirst-row second conductive layer W11 (word line WL1), a current flowsin the first-layer first-row memory cell CE11.

For instance, When a voltage VR lower than the voltage VT is appliedbetween the first-layer first-row first conductive layer B11 (bit lineBL) and the first-layer first-row second conductive layer W11 (word lineWL1), a current is harder to flow in the first-layer first-row memorycell CE11. In the first-layer first-row memory cell CE11, the magnitudeof the current changes in response to the applied voltage.

A thickness t2 of the second-layer first-row second conductive layer W21along the third direction Dr3 is larger than a thickness t1 of thefirst-layer first-row second conductive layer W11 along the thirddirection Dr3.

The first-layer first-row second conductive layer W11 includes a firstportion W11 a, a second portion W11 b, and the third portion W11 cprovided between the first portion W11 a and the second portion W11 b.The third portion W11 c is connected to the first-layer first-rowcontact CT11.

A first distance D1 of the first portion W11 a along the seconddirection Dr2 is nearly equal to a second distance D2 of the secondportion W11 b along the second direction Dr2. The first distance D1 ise.g. 0.8 to 1.2 times the second distance D2.

The semiconductor memory device 110 according to the embodiment furtherincludes a first-layer third-row first conductive layer B13, afirst-layer fourth-row first conductive layer B14, a first-layerthird-row memory cell CE13, a first-layer fourth-row memory cell CE14, afirst-layer third-row second conductive layer W13, a first-layerthird-row contact CT13, a second-layer third-row intermediate memorycell MC23, a second-layer third-row first conductive layer B23, and asecond-layer third-row memory cell CE23.

The first-layer fourth-row first conductive layer B14 is separated fromthe first-layer second-row first conductive layer B12 in the seconddirection Dr2 and extends in the first direction Dr1. The first-layerthird-row first conductive layer B13 is provided between the first-layerfourth-row first conductive layer B14 and the second-layer second-rowcontact CT22 and extends in the first direction Dr1.

The first-layer third-row second conductive layer W13 is separated fromthe first-layer third-row first conductive layer B13 and the first-layerfourth-row first conductive layer B14 in the third direction Dr3,separated from the first-layer first-row second conductive layer W11 inthe second direction Dr2, and extends in the second direction Dr2.

The first-layer third-row memory cell CE13 is provided between thefirst-layer third-row second conductive layer W13 and the first-layerthird-row first conductive layer B13. The first-layer fourth-row memorycell CE14 is provided between the first-layer third-row secondconductive layer W13 and the first-layer fourth-row first conductivelayer B14.

The first-layer third-row contact CT13 is connected to the first-layerthird-row second conductive layer W13. The first-layer third-row contactCT13 extends in the third direction Dr3 between the first-layerthird-row first conductive layer B13 and the first-layer fourth-rowfirst conductive layer B14.

The second-layer third-row intermediate memory cell MC23 is providedbetween the first-layer third-row second conductive layer W13 and thesecond-layer first-row second conductive layer W21. The second-layerthird-row first conductive layer B23 is provided between thesecond-layer third-row intermediate memory cell MC23 and thesecond-layer first-row second conductive layer W21 and extends in thefirst direction. The second-layer third-row memory cell CE23 is providedbetween the second-layer third-row first conductive layer B23 and thesecond-layer first-row second conductive layer W21.

The second-layer second-row contact CT22 is disposed between thefirst-layer first-row second conductive layer W11 and the first-layerthird-row second conductive layer W13. The second-layer second-rowcontact CT22 is disposed between the second-layer first-row intermediatememory cell MC21 and the second-layer third-row intermediate memory cellMC23. The second-layer second-row contact CT22 is disposed between thesecond-layer first-row first conductive layer B21 and the second-layerthird-row first conductive layer B23. The second-layer second-rowcontact CT22 is disposed between the second-layer first-row memory cellCE21 and the second-layer third-row memory cell CE23.

The second-layer first-row second conductive layer W21 includes a fourthportion W21 d, a fifth portion W21 e, and a sixth portion W21 f providedbetween the fourth portion W21 d and the fifth portion W21 e. The sixthportion W21 f is connected to the second-layer second-row contact CT22.

A fourth distance D4 of the fourth portion W21 d along the seconddirection Dr2 is nearly equal to a fifth distance D5 of the fifthportion W21 e along the second direction Dr2. The fourth distance D4 ise.g. 0.8 to 1.2 times the fifth distance D5.

The semiconductor memory device 110 according to the embodiment furtherincludes a first transistor TR1, a second transistor TR2, and a thirdtransistor TR3. The first transistor TR1 is electrically connected tothe first-layer first-row contact CT11. The second transistor TR2 iselectrically connected to the second-layer second-row contact CT22. Thethird transistor TR3 is electrically connected to the first-layerthird-row contact CT13.

As described above, the semiconductor memory device 110 according to theembodiment includes a plurality of the first blocks BK1, a plurality ofthe second blocks BK2, the third block BK3, and the fourth block BK4.The plurality of first blocks BK1 are arranged in the second directionDr2. The plurality of second blocks BK2 are arranged in the seconddirection Dr2.

One of the plurality of first blocks BK1 includes e.g. the first-layerfirst-row first conductive layer B11, the first-layer second-row firstconductive layer B12, the first-layer first-row memory cell CE11, thefirst-layer second-row memory cell CE12, the first-layer first-rowsecond conductive layer W11, and the first-layer first-row contact CT11.

One of the plurality of second blocks BK2 includes e.g. the second-layerfirst-row intermediate memory cell MC21, the second-layer first-rowfirst conductive layer B21, the second-layer first-row memory cell CE21,the second-layer first-row second conductive layer W21, the second-layersecond-row contact CT22, the second-layer third-row intermediate memorycell MC23, the second-layer third-row first conductive layer B23, andthe second-layer third-row memory cell CE23.

In the embodiment, for instance, when a 1000 bit lines respectivelyextend in the first direction Dr1 and are arranged in the seconddirection Dr2, the 1000 bit lines are divided in five regions. Oneregion includes 200 bit lines. The distance between the 200th bit lineand the 201st bit line is larger than the distance between the first bitline and the second bit line. The contact is provided between the 200thbit line and the 201st bit line.

In a cross-point memory such as ReRAM (Resistance Random Access Memory),as the number of memory cells is larger, the lengths of the bit linesand the word lines are larger. When voltages are applied from thetransistors to the bit lines and the word lines, if the lengths of thebit lines and the word lines are larger, the voltages applied to thememory cells become non-constant due to reduction of the voltages.Thereby, fluctuations of the voltages applied to the memory cells may belarger.

In this regard, in the semiconductor memory device 110 according to theembodiment, the first length L1 of the first-layer first-row secondconductive layer W11 along the second direction Dr2 is shorter than thesecond length L2 of the second-layer first-row second conductive layerW21 along the second direction Dr2.

When a voltage is applied between the first-layer first-row firstconductive layer B11 and and the first-layer first-row second conductivelayer W11, the reduction of the voltage is small. Thereby, for instance,the voltages applied to the memory cells (CE11, CE12) in a first layer1L are more equalized than the voltages applied to the memory cells(CE21, CE22, CE23, CE24) in a second layer 2L. That is, the fluctuationsof the voltages applied to the memory cells become smaller.

As a result, it is possible to provide a semiconductor memory devicethat can improve operation stability.

In the semiconductor memory device 110 according to the embodiment, alayer including the first-layer first-row second conductive layer W11,the first-layer third-row second conductive layer W13, the first-layerfirst-row contact CT11, and the first-layer third-row contact CT13 ise.g. the first layer 1L. A layer including the second-layer first-rowsecond conductive layer W21 and the second-layer second-row contact CT22is e.g. the second layer 2L.

The first-layer first-row second conductive layer W11 and the firsttransistor TR1 are electrically connected, and the first-layer third-rowsecond conductive layer W13 and the third transistor TR3 areelectrically connected. The second-layer first-row second conductivelayer W21 and the second transistor TR2 are electrically connected.

The number of transistors electrically connected to the second layer 2Lis smaller than the number of transistors electrically connected to thefirst layer 1L. For instance, the number of transistors electricallyconnected to the second layer 2L is a half of the number of transistorselectrically connected to the first layer 1L. Thereby, it is possible tosecure operation stability in the upper layers farther from thesubstrate in which the operation is likely to be unstable. Since thenumber of transistors is smaller, power consumption may be lower.Further, the device is miniaturized.

The third layer (third block BK3) and the fourth layer (fourth blockBK4) have e.g. the same configurations as the above described firstlayer (first block BK1) and the second layer (second block BK2).

FIG. 2A is a schematic sectional view illustrating the semiconductormemory device according to the embodiment.

FIG. 2A is the schematic sectional view along line C1-C2 in FIG. 1A.

As shown in FIG. 2A, the semiconductor memory device 110 according tothe embodiment further includes a plurality of fifth-layer firstconductive layers B5, a plurality of fourth-layer first-row secondconductive layers W41, a plurality of fourth-layer first-row contactsCT41, a plurality of fourth-layer eighth-row contacts CT48, and aplurality of fifth-layer contacts CTB5. The respective fifth-layer firstconductive layers B5 and the respective fourth-layer first-row secondconductive layers W41 cross.

One end of each fourth-layer first-row second conductive layer W41 isconnected to one of the plurality of fourth-layer first-row contactsCT41. The other end of each fourth-layer first-row second conductivelayer W41 is connected to one of the plurality of fourth-layereighth-row contacts CT48. One end of each fifth-layer first conductivelayer B5 is connected to one of the plurality of fifth-layer contactsCTB5.

The respective plurality of fifth-layer first conductive layers B5extend in the first direction Dr1. The respective plurality offourth-layer first-row second conductive layers W41 extend in the seconddirection Dr2. The respective plurality of fifth-layer contacts CTB5extend in the third direction Dr3. The respective plurality offourth-layer eighth-row contacts CT48 extend in the third direction Dr3.

FIG. 2B is a schematic sectional view illustrating the semiconductormemory device according to the embodiment.

FIG. 2B is the schematic sectional view along line F1-F2 in FIG. 1A.

As shown in FIG. 2B, the semiconductor memory device 110 according tothe embodiment further includes a plurality of fourth-layer firstconductive layers B4, a plurality of third-layer first-row secondconductive layers W31, a plurality of fourth-layer contacts CTB4, and aplurality of third-layer fourth-row contacts CT34. The respectivefourth-layer first conductive layers B4 and the respective third-layerfirst-row second conductive layers W31 cross.

One of the plurality of third-layer first-row second conductive layersW31 and one of the plurality of third-layer fourth-row contacts CT34 areconnected. One of the plurality of fourth-layer first conductive layersB4 and one of the plurality of fourth-layer contacts CTB4 are connected.

The respective plurality of fourth-layer first conductive layers B4extend in the first direction Dr1. The respective plurality ofthird-layer first-row second conductive layers W31 extend in the seconddirection Dr2. The respective plurality of fourth-layer contacts CTB4extend in the third direction Dr3. The respective plurality ofthird-layer fourth-row contacts CT34 extend in the third direction Dr3.

FIG. 3A is a schematic sectional view illustrating the semiconductormemory device according to the embodiment.

FIG. 3A is the schematic sectional view along line G1-G2 in FIG. 1A.

As shown in FIG. 3A, the semiconductor memory device 110 according tothe embodiment further includes a plurality of third-layer firstconductive layers B3, a plurality of second-layer first-row secondconductive layers W21, and a plurality of second-layer second-rowcontacts CT22. The respective third-layer first conductive layers B3 andthe respective second-layer first-row second conductive layers W21cross.

One of the plurality of second-layer first-row second conductive layersW21 and one of the second-layer second-row contacts CT22 are connected.One end of each of the respective third-layer first conductive layers B3is connected to one of the plurality of fifth-layer contacts CTB5.

The respective plurality of third-layer first conductive layers B3extend in the first direction Dr1. The respective plurality ofsecond-layer first-row second conductive layers W21 extend in the seconddirection Dr2. The respective plurality of second-layer second-rowcontacts CT22 extend in the third direction Dr3.

The semiconductor memory device 110 according to the embodiment furtherincludes a plurality of second-layer fifth-row second conductive layersW25 and a plurality of second-layer sixth-row contacts CT26. Therespective third-layer first conductive layers B3 and the respectivesecond-layer fifth-row second conductive layers W25 cross.

One of the plurality of second-layer fifth-row second conductive layersW25 and one of the plurality of second-layer sixth-row contacts CT26 areconnected.

The respective plurality of second-layer fifth-row second conductivelayers W25 extend in the second direction Dr2. The respective pluralityof second-layer sixth-row contacts CT26 extend in the third directionDr3.

FIG. 3B is a schematic sectional view illustrating the semiconductormemory device according to the embodiment.

FIG. 3B is the schematic sectional view along line H1-H2 in FIG. 1A.

As shown in FIG. 3B, the semiconductor memory device 110 according tothe embodiment further includes a plurality of second-layer first-rowfirst conductive layers B21, a plurality of second-layer second-rowfirst conductive layers B22, a plurality of first-layer first-row secondconductive layers W11, and a plurality of first-layer first-row contactsCT11.

The respective second-layer first-row first conductive layers B21 andthe respective first-layer first-row second conductive layers W11 cross.The respective second-layer second-row first conductive layers B22 andthe respective first-layer first-row second conductive layers W11 cross.One of the plurality of first-layer first-row second conductive layersand one of the plurality of first-layer first-row contacts CT11 areconnected. One of the plurality of second-layer first-row firstconductive layers B21 and one of the plurality of fourth-layer contactsCTB4 are connected.

The respective plurality of second-layer first-row first conductivelayers B21 extend in the first direction Dr1. The respective pluralityof second-layer second-row first conductive layers B22 extend in thefirst direction Dr1. The respective plurality of first-layer first-rowsecond conductive layers W11 extend in the second direction Dr2. Therespective plurality of first-layer first-row contacts CT11 extend inthe third direction Dr3.

The semiconductor memory device 110 according to the embodiment furtherincludes a plurality of second-layer third-row first conductive layersB23, a plurality of second-layer fourth-row first conductive layers B24,a plurality of first-layer third-row second conductive layers W13, and aplurality of first-layer third-row contacts CT13.

The respective second-layer third-row first conductive layers B23 andthe respective first-layer third-row second conductive layers W13 cross.The respective second-layer fourth-row first conductive layers B24 andthe respective first-layer third-row second conductive layers W13 cross.One of the plurality of first-layer third-row second conductive layersW13 and one of the plurality of first-layer third-row contacts CT13 areconnected. One of the plurality of second-layer third-row firstconductive layers B23 and one of the plurality of fourth-layer contactsCTB4 are connected.

The respective plurality of second-layer third-row first conductivelayers B23 extend in the first direction Dr1. The respective pluralityof second-layer fourth-row first conductive layers B24 extend in thefirst direction Dr1. The respective plurality of first-layer third-rowsecond conductive layers W13 extend in the second direction Dr2. Therespective plurality of first-layer third-row contacts CT13 extend inthe third direction Dr3.

FIG. 4 is a schematic sectional view illustrating the semiconductormemory device according to the embodiment.

FIG. 4 is the schematic sectional view along line 31-32 in FIG. 1A.

As shown in FIG. 4 , the semiconductor memory device 110 according tothe embodiment further includes a plurality of first-layer first-rowfirst conductive layers B11, a plurality of first-layer first-row secondconductive layers B12, a plurality of first-layer third-row firstconductive layers B13, and a plurality of first-layer first-row fourthconductive layers B14.

The respective pluralities of first-layer first-row to fourth-row firstconductive layers B11 to B14 extend in the first direction Dr1.

FIG. 5 is a schematic sectional view of another example of thesemiconductor memory device according to the embodiment.

As shown in FIG. 5 , in a semiconductor memory device 120 according tothe embodiment, a plurality of third-layer first-row contacts CT31 areprovided in place of the plurality of fourth-layer first-row contactsCT41. A plurality of third-layer eighth-row contacts CT38 are providedin place of the plurality of fourth-layer eighth-row contacts CT48. Aplurality of fourth-layer fourth-row contacts CT44 are provided in placeof the plurality of third-layer fourth-row contacts CT34. A plurality ofthird-layer second-row second conductive layers W32 and a plurality ofthird-layer fifth-row second conductive layers W35 are provided in placeof the plurality of third-layer first-row second conductive layers W31.

The respective plurality of third-layer fifth-row second conductivelayers W35 are arranged with the respective plurality of third-layersecond-row second conductive layers W32 in the second direction Dr2. Oneof the plurality of fourth-layer fourth-row contacts CT44 is providedbetween one of the plurality of third-layer second-row second conductivelayers W32 and one of the plurality of third-layer fifth-row secondconductive layers W35. One of the plurality of fourth-layer first-rowsecond conductive layers W41 and one of the plurality of fourth-layerfourth-row contacts CT44 are connected. One end of one of the pluralityof third-layer second-row second conductive layers W32 and one of theplurality of third-layer first-row contacts CT31 are connected. One endof one of the plurality of third-layer fifth-row second conductivelayers W35 and one of the plurality of third-layer eighth-row contactsCT38 are connected.

The fourth-layer first-row second conductive layers W41, the third-layersecond-row second conductive layers W32, and the third-layer fifth-rowsecond conductive layers W35 are e.g. word lines. The word line with oneend connected to the contact is not necessarily the word line in theuppermost layer, e.g., W41 shown in FIG. 5 . One end of the word line inthe second layer from the top e.g. the third-layer second-row secondconductive layer W32 and the contact may be connected. For instance, oneend of the third-layer fifth-row second conductive layer W35 and thecontact may be connected.

According to the embodiment, it is possible to provide a semiconductormemory device capable of improving operation stability.

Various other variations and modifications can be conceived by thoseskilled in the art within the spirit of the invention, and it isunderstood that such variations and modifications are also encompassedwithin the scope of the invention.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the invention.

What is claimed is:
 1. A semiconductor memory device comprising: afirst-layer first-row first conductive layer extending in a firstdirection; a first-layer second-row first conductive layer separatedfrom the first-layer first-row first conductive layer in a seconddirection crossing the first direction and extending in the firstdirection; a first-layer first-row second conductive layer separatedfrom the first-layer first-row first conductive layer and thefirst-layer second-row first conductive layer in a third directioncrossing the first direction and crossing the second direction andextending in the second direction; a first-layer first-row memory cellprovided between the first-layer first-row second conductive layer andthe first-layer first-row first conductive layer; a first-layersecond-row memory cell provided between the first-layer first-row secondconductive layer and the first-layer second-row first conductive layer;a first-layer first-row contact connected to the first-layer first-rowsecond conductive layer and extending in the third direction between thefirst-layer first-row first conductive layer and the first-layersecond-row first conductive layer; a second-layer first-row secondconductive layer separated from the first-layer first-row secondconductive layer in the third direction and extending in the seconddirection, the first-layer first-row second conductive layer beingdisposed between the second-layer first-row second conductive layer andthe first-layer first-row memory cell and between the second-layerfirst-row second conductive layer and the first-layer second-row memorycell in the third direction; a second-layer first-row intermediatememory cell provided between the first-layer first-row second conductivelayer and the second-layer first-row second conductive layer; asecond-layer first-row first conductive layer provided between thesecond-layer first-row intermediate memory cell and the second-layerfirst-row second conductive layer and extending in the first direction;a second-layer first-row memory cell provided between the second-layerfirst-row first conductive layer and the second-layer first-row secondconductive layer; and a second-layer second-row contact connected to thesecond-layer first-row second conductive layer, separated from thefirst-layer first-row contact in the second direction, and extending inthe third direction, the first-layer second-row first conductive layerand the first-layer second-row memory cell being disposed between thesecond-layer second-row contact and the first-layer first-row contact inthe second direction, a first length of the first-layer first-row secondconductive layer along the second direction being shorter than a secondlength of the second-layer first-row second conductive layer along thesecond direction.
 2. The device according to claim 1, furthercomprising: a first-layer fourth-row first conductive layer separatedfrom the first-layer second-row first conductive layer in the seconddirection and extending in the first direction; a first-layer third-rowfirst conductive layer provided between the first-layer fourth-row firstconductive layer and the second-layer second-row contact and extendingin the first direction, a first-layer third-row second conductive layerseparated from the first-layer third-row first conductive layer and thefirst-layer fourth-row first conductive layer in the third direction,separated from the first-layer first-row second conductive layer in thesecond direction, and extending in the second direction, thesecond-layer second-row contact being disposed between the first-layerfirst-row second conductive layer and the first-layer third-row secondconductive layer; a first-layer third-row memory cell provided betweenthe first-layer third-row second conductive layer and the first-layerthird-row first conductive layer; a first-layer fourth-row memory cellprovided between the first-layer third-row second conductive layer andthe first-layer fourth-row first conductive layer; a first-layerthird-row contact connected to the first-layer third-row secondconductive layer and extending in the third direction between thefirst-layer third-row first conductive layer and the first-layerfourth-row first conductive layer; a second-layer third-row intermediatememory cell provided between the first-layer third-row second conductivelayer and the second-layer first-row second conductive layer, thesecond-layer second-row contact being disposed between the second-layerfirst-row intermediate memory cell and the second-layer third-rowintermediate memory cell; a second-layer third-row first conductivelayer provided between the second-layer third-row intermediate memorycell and the second-layer first-row second conductive layer andextending in the first direction, the second-layer second-row contactbeing disposed between the second-layer first-row first conductive layerand the second-layer third-row first conductive layer; and asecond-layer third-row memory cell provided between the second-layerthird-row first conductive layer and the second-layer first-row secondconductive layer, the second-layer second-row contact being disposedbetween the second-layer first-row memory cell and the second-layerthird-row memory cell.
 3. The device according to claim 1, wherein athickness of the second-layer first-row second conductive layer alongthe third direction is larger than a thickness of the first-layerfirst-row second conductive layer along the third direction.
 4. Thedevice according to claim 1, wherein the first-layer first-row secondconductive layer includes a first portion, a second portion, and a thirdportion provided between the first portion and the second portion, thethird portion is connected to the first-layer first-row contact, and afirst distance of the first portion along the second direction is 0.8 to1.2 times a second distance of the second portion along the seconddirection.
 5. The device according to claim 1, wherein the second-layerfirst-row second conductive layer includes a fourth portion, a fifthportion, and a sixth portion provided between the fourth portion and thefifth portion, the sixth portion is connected to the second-layersecond-row contact, and a fourth distance of the fourth portion alongthe second direction is 0.8 to 1.2 times a fifth distance of the fifthportion along the second direction.
 6. The device according to claim 1,further comprising: a first transistor (TR1) electrically connected tothe first-layer first-row contact; and a second transistor (TR2)electrically connected to the second-layer second-row contact.
 7. Thedevice according to claim 2, further comprising a third transistorelectrically connected to the first-layer third-row contact.
 8. Thedevice according to claim 1, further comprising: a first-layer first-rowposterior first conductive layer separately provided from thefirst-layer first-row first conductive layer in the first direction andextending in the first direction; a fourth-layer first-row intermediatecontact provided between the first-layer first-row first conductivelayer and the first-layer first-row posterior first conductive layer,extending in the third direction, and electrically connected to thesecond-layer first-row first conductive layer; a fourth-layer first-rowanterior contact extending in the third direction and electricallyconnected to the first-layer first-row first conductive layer, thefirst-layer first-row first conductive layer being disposed between thefourth-layer first-row anterior contact and the fourth-layer first-rowintermediate contact; and a fourth-layer first-row posterior contactextending in the third direction and electrically connected to thefirst-layer first-row posterior first conductive layer, the first-layerfirst-row posterior first conductive layer being disposed between thefourth-layer first-row posterior contact and the fourth-layer first-rowintermediate contact.
 9. A semiconductor memory device comprising: aplurality of bit lines extending in a first direction; a plurality ofword lines extending in a second direction crossing the first direction,the plurality of word lines alternately being arranged with theplurality of bit lines in a third direction crossing the first directionand crossing the second direction; and a memory cell provided betweenone of the plurality of bit lines and one of the plurality of wordlines, a length along the first direction of another one of the bitlines disposed separately from the one of the bit lines in the thirddirection being larger than a length of the one of the bit lines alongthe first direction, or a length along the first direction of anotherone of the word lines disposed separately from the one of the word linesin the third direction being larger than a length of the one of the wordlines along the first direction.
 10. The device according to claim 9,further comprising: a bit line contact extending in the third directionand electrically connected to the other one of the plurality of bitlines; and a word line contact extending in the third direction andelectrically connected to the other one of the plurality of word lines,the plurality of bit lines including still another one of the pluralityof bit lines separated from the one of the plurality of bit lines in thefirst direction, the plurality of word lines including still another oneof the plurality of word lines separated from the one of the pluralityof word lines in the second direction; the bit line contact beingdisposed between the one of the plurality of bit lines and the stillother one of the plurality of bit lines, or the word line contact beingdisposed between the one of the plurality of word lines and the stillother one of the plurality of word lines.
 11. The device according toclaim 9, further comprising: an intermediate contact; an anteriorcontact; and a posterior contact, the plurality of bit lines includingstill another one of the plurality of bit lines separately provided fromthe one of the plurality of bit lines in the first direction andextending in the first direction; the intermediate contact beingprovided between the one of the plurality of bit lines and the stillother one of the plurality of bit lines, extending in the thirddirection, and electrically connected to the other one of the bit lines;the anterior contact extending in the third direction and electricallyconnected to the one of the plurality of bit lines, the one of theplurality of bit lines being disposed between the anterior contact andthe intermediate contact; and the posterior contact extending in thethird direction and electrically connected to the still other one of theplurality of bit lines, the still another one of the plurality of bitlines being disposed between the posterior contact and the intermediatecontact.